Two substantial dance productions set the seal on this year's Edinburgh festival. For the first of these, Balanchine's Don Quixote, audience enthusiasm was restrained. Rambling and episodic, ponderously reliant on stage effects, it seemed to abandon all the modernist principles which illuminate the choreographer's earlier work. How could the creator of the arctically elegant Serenade (1934), or the tautly ambiguous Agon (1957), have compromised his vision in this way?

The ballet follows Cervantes' tale of the Don and his wanderings in search of knight-errantry. His consistent misreading of events, however, earns him only ridicule. At a ducal palace, bored aristocrats amuse themselves by humiliating him, and when they finally throw him out, the Don tilts at the famous windmills. Fatally injuring himself, he dies.

At each stage of the story young women appear - a servant girl, a shepherdess, imaginary spirit maidens - and in the Don's disordered mind these all become one: his muse, his ideal, his Dulcinea. It is in these episodes that the ballet's intentions reveal themselves. The piece is a confessional, and perhaps the most personal ballet the choreographer ever created. Balanchine spent his life in pursuit of his own perfect muse, marrying and divorcing several of his ballerinas in the process, and by 1964, when work on Don Quixote began, he was convinced that he had found her. She was Suzanne Farrell, then a brilliant 19-year-old principal with New York City Ballet. In awe of his genius, Farrell was happy to serve as Balanchine's artistic ideal, and with her willowy figure and racy, off-classical style, went on to create many of his greatest roles - perhaps most memorably the scintillating Diamond fairy in Jewels (1967). Given the 40-year age gap between them, and for all the rich intimacy of their creative relationship, Farrell was unable to return her mentor's feelings, and insisted that their association remained platonic.

In the light of these events, Balanchine's passionate attachment to Cervantes' tale begins to make sense. Don Quixote, in which he and Farrell played the leading roles, is Balanchine's cri de coeur, his expression of the intensity but ultimate hopelessness of his love for his own Dulcinea. The self-portrait is as unsparing as the plot suggests, with the Don the butt of every situation. At one point, in a revealing metaphor for the male sexual appetite, Dulcinea leads him around by the beard.

Tellingly, Balanchine left this production to Farrell when he died in 1983. Three years after its opening, unable to manage the tensions and ambiguities of her relationship with him, she had left New York City Ballet to work in Europe. She retired from the stage in 1989. Now 61 (Balanchine's age when Don Quixote opened), Farrell has remounted the ballet, largely from her own memory, and in so doing rescripted for a new generation this most anguished of love poems to herself.

And while it remains deeply flawed, and in narrative terms plays to all Balanchine's weaknesses - his heavy hand with formal divertissements, the over-reliance on the freakish which is echoed in Prodigal Son, his unspontaneous way with ensemble work (vide A Midsummer Night's Dream) - something darkly powerful still glowers about this work. Balanchine awards Dulcinea two defining solos. The first, a masterpiece of fantasy-bizarre, is the shepherdess dance in Act II, composed of surreal struts and poses. The second, in the final act, is an unbroken stream of movement, all reaching arms, flyaway turns and oblique, off-centre balances. Heather Ogden, while clearly lacking the extreme plasticity which made Farrell so unforgettable, negotiates the role with brisk technical competence and sounds a precise note of sweet, sad unattainability. As the Don, Momchil Mladenov is impressive when motionless but dodders too much, undercutting the character's pathos with comedy-grandfather creakiness. In general, Farrell's company acquit themselves well, but there are problems of basic stagecraft. Pirouettes and jettes are all very well, but you need to be able to walk across the stage, as the men do in the Don's death scene, without looking as if you've just had haemorrhoid surgery. This bathetic procession, coupled with a stage mechanism which causes Quixote to levitate sharply at the moment of expiry, somewhat compromises the solemnity of the ballet's final moments.

A sense of deja vu, meanwhile, as Nederlands Dans Theater 1 present a programme of work by resident choreographers Paul Lightfoot and Sol Leon. In Silent Screen, dancers perform a kind of hyper-extended semaphore in front of a black-and-white film with which they interact. The music, somewhat inevitably, is by Philip Glass.

The dancing is stunning, particularly that of Parvaneh Scharafali and Jorge Nozal, the lead couple, and the staging extraordinarily beautiful, with the tall, dark forms of the dancers incised against the silvery wash of the film. And as in most NDT programmes there comes a point, as in a Versace promotion, when the sheer extravagance of the styling overwhelms the possibility of meaning; when the work's lush surface becomes its only subject. But then who wouldn't be seduced by dancing of this calibre, or by black silk curtains billowing out like giant tulip petals over the auditorium, or by the whole NDT schtick? It's not profound, but then neither is eating caviar in a sunken marble bath. Just consume and enjoy. I promise you won't feel bad afterwards. To be honest, I doubt you will feel anything at all.